Just because he's tiny doesn't mean he can't go outside. As long as he's got all of his shots and you're supervising, I don't see a problem with it. I never understood that logic, lol, he's still a dog! And ya never know how big he may get! I've read stories on here of people who picked the smallest in the litter and they ended up being over 5 pounds, etc and sometimes bigger.
But anyways, yeah 10 weeks is young. Jackson's 5 months and I would say he's 98% potty trained. Yorkies are known to take up to a year to potty train. You just have to be very consistent, keep them on the same schedule every day, they will always have to go after drinking water or eating food. Never take your eye off of him. Keep him in a confined area. Treat and praise everytime he goes where he's supposed to.
There's a really good thread on here somewhere about potty training and I can't find it. If you go to "Search" you can type in potty training and I'm sure you'll find a lot!